Wireless communication has undergone a tremendous development in the last decade. With the evolution and development of wireless networks towards 3G-and-beyond, packet data services have been the major focus with the aim to provide e.g. higher bandwidth and accessibility to the Internet. Hence, protocols and network architectures including end user devices and terminals are normally designed and built to support Internet Protocol (IP) services as efficiently as possible.
For example, the evolution of the WCDMA specification with High Speed Downlink Packet Access (HSDPA) in the downlink and Enhanced Dedicated Channel (E-DCH) in the uplink provides an air interface that has been optimized to transmit IP packets over the WCDMA radio access interface. This has lead to a possibility of providing also conversational services (media applications) over IP with high spectrum efficiency (comparable or even exceeding the performance of existing circuit switched conversational bearers). FIG. 1 illustrates relevant parts of a simplified radio communication system with a base station 100 such as a Node B in communication with user equipment (UE) 200 over the traditional downlink and uplink. The UE 200 implements an IP stack according to accepted standard technology. The protocol stack normally involves the physical layer, the data link layer, the network layer, the transport layer and the application layer. In the case of an IP stack, the network layer is based on IPv4 or IPv6, or mobile counterparts such as MIPv4 or MIPv6, and is often simply referred to as the IP layer or the Internet layer.
The conversational services may consist of various service or application components, such as voice, video or text based communication. Each service component has different requirements regarding minimum usable data rate, possibility to adapt to variation in the data rate, allowed delay and packet loss, etc. The communication application may adapt to changes in various ways, for example:                Voice codecs based on AMR may use different modes resulting in different applications.        The number of service components for an application may be reduced, e.g. by deciding to drop the video component and only keep voice.        
E-DCH provides a dedicated channel that has been enhanced for IP transmission, as specified in the standardization documents 3GPP TS 25.309 and TS 25.319. The enhancements include:                Possibility to use a shorter TTI (Transmission Time Interval).        Fast hybrid ARQ (HARQ) between mobile terminal and the base station.        Scheduling of the transmission rates of mobile terminals from the base station.        
Similarly to HSDPA in the downlink, there will be a packet scheduler for E-DCH in the uplink, but it will normally operate on a request-grant principle, where the user equipment (UE) or terminal requests a permission to send data and the scheduler on the network side decides when and how many terminals will be allowed to do so. A request for transmission will normally contain data about the state of the transmission data buffer and the queue at the terminal side and its available power margin. The standard foresees two basic scheduling methods. Long term grants are issued to several terminals which can send their data simultaneously using code multiplexation. Short term grants on the other hand allow multiplexing of terminals in the time domain. In order to allow multiplexing uplink transmissions of several terminals in both code and time domain the scrambling and channelization codes are expected to not be shared between different terminals.
Assuming that the dedicated physical data channel (DPDCH) and the dedicated physical control channel (DPCCH) are code-multiplexed and transmitted simultaneously in time, the ratio between their transmit powers is important for the achievable payload data rates. When a larger part of the terminal's power is assigned to DPDCH the achievable payload data rate increases. In UMTS Release 99 the ratio between the power of DPDCH and DPCCH was set to a constant value. For E-DCH, this ratio will generally be controlled by the base station (Node B) and signaled to the terminals in the scheduling grant commands.
When using E-DCH or similar uplink technology, there are two mechanisms that can restrict the data rate of an individual UE. First, the base station may lower the current data rate of the UE by updating the serving grant (i.e. by scheduling). Second, the UE may not have sufficient transmission power to maintain the current data rate, in which case the UE will automatically limit the transmission rate. This autonomous reduction typically occurs when the UE is close to the edge of the cell.
Similarly, the rate of an individual UE may be increased by updating the serving grant from the Node B, or—if the UE was power limited—it may increase the rate autonomously as soon as sufficient power comes available.
Reducing the link data rate may lead to problems with conversational applications. In general, if the data rate of an application exceeds the link data rate, packets will be first buffered and eventually (once the buffers overflow) dropped. The buffering leads to increased transmission delay, and reduced conversational quality, while the packet losses lead directly to reduced quality.
When increasing the link rate, it would be possible for the application to improve the quality by e.g. increasing the data rate or by adding new service components to the call. However, the application needs to probe (e.g. by trying to increase the transmission rate and observing the resulting packet loss and/or delay) for the available bandwidth before improving the quality. This probing mechanism needs to be conservative in order to avoid increasing load in congested situation, which makes it necessarily slow.
Using link quality measures such as end-to-end packet loss or received signal strength, will generally lead to both late detection of the rate change of E-DCH or similar uplink channel and limited possibility to detect the new link data rate.
Late detection of the rate change will result in packets being queued by the E-DCH link layer. The queuing leads to increased conversational delay or late losses.
In general, using a probing mechanism to detect increase in the available data rate leads to both slow recovery from reduced link rate and slow reaction to available high data rate. Furthermore, all probing mechanisms may increase the load in congested situations and thus reduce the performance.
Estimating the link data rate too high will again lead to queuing and/or packet loss. Estimating the link data rate too low will lead to too low application data rate being used. This in general results in worse (speech) quality.
There is thus a general demand for improving the performance of an uplink channel between user equipment and a base station in a wireless communication system.